Safety slow-down device for hydraulic elevators

ABSTRACT

The outer casing of a hydraulic elevator is internally provided with a tubular column extending upwardly from the lower casing head into the tubular ram. Orifice ports in the tubular column equalize the pressures in the ram and the casing externally of the ram. These ports progressively restrict pressure equalizing flow as the ram descends under load to limit the descent rate of the ram.

[ 1 Nov. 27, 1973 United States Patent McCreery okun mw mmmm cy om 7004 5666 9999 mm 3 98 46 -4 8,M38 W V Z 2223 R U 0 ll F m E 18 m m m D R C a 0 c Wm MA 0 B mmnm w mm 06 mm RB SL v w n TR w ED n F e A Y m SH] H N U U Xenia Ohio 45385 Primary Examiner-Paul E. Maslousky Aug, ,17, 1971 Att0rneyOBn'en & Jacobson Appl. No.: 172,388

[22] Filed:

[57] ABSTRACT The outer casing of a hydraulic elevator is internally provided with a tubular column extending upwardly from the lower casing head into the tubular ram. Ori- 91 Q5, 26, 405 415 fice ports 1n the tubular column equalize the pressures in the ram and the casing externally of the ram. These ports progressively restrict pressure equalizing flow as [56] References Cited UNITED STATES PATENTS the ram descends under load to limit the descent rate of the ram.

91/25 17 Claims, 8 Drawing Figures This invention relates to a safety device for fluid operated elevators or the like, and more particularly to a device for decelerating a downwardly descending fluid pressure ram in the event there is a sudden loss in pressure due to uncontrolled leakage of fluid from the cylinder into which the ram is descending.

Hydraulic elevators of the type with which the present invention is concerned, consist essentially of an outside pressure casing having a pressure sealed head at the bottom and an upper guide bearing with seals in wiping engagement with a vertically rising ram extended from the casing by the introduction of pressurized fluid into the cylinder cavity. The ram is lowered or retracted into the cylinder casing by controlled release of fluid pressure and the rate of descent will be a function of the flow rate of the fluid exiting from the cylinder casing cavity. In the event there is some unintended leakage of fluid from the cylinder casing due to casing corrosion or leakage from a rupturedsupply line extending between the cylinder casing and the source of fluid, there will be uncontrolled fall or descent of the hydraulic ram which could cause considerable damage depending on the load supported on the top of the ram.

FIG. 6 is a partial side sectional view showing the hydraulic device in a ram descending phase of operation;

FIG. 7 is a schematic sectional view through a typical installation within which the present invention is utilized; and

FIG. 8 is a partial side sectional view through one of the safety slow-down devices shown in FIG. 7 constituting a modification of the arrangement shown in FIG. 2.

Referring now the drawings in detail and initially to FIGS. 1 and 2, the hydraulic device generally referred to by reference numeral 10 represents one installation with which the present invention is associated. The hy- It is therefore an important object of the present invention to decelerate the descent of the ram in order to prevent injury or damage should there be any uncontrolled leakage of pressurized fluid from the cylinder cavity or the fluid line connected thereto.

In accordance with the present invention, the hydraulic ram is of tubular construction and encloses a pressure chamber therein. The ram is positioned internally over a tubular column fixed to the cylinder casing. Orifice ports are formed in the tubular column in order to conduct pressure equalizing flow of fluid between the pressure chamber of the ram and the cylinder cavity without affecting normal displacement of the ram of a piston in response to controlled pressurization and depressurization of the cylinder cavity. The orifice ports formed in the tubular column are dimensionally arranged so as to progressively increase restriction to pressure equalizing flow as the ram descends. Accord ingly, the rate of descent of the ram will be limited so as to decelerate downward movement of the ram which the present invention is associated;

FIG. 2 is a side sectional view taken substantially on a plane indicated by section line 2-2 in FIG. 1;

FIG. 3 is a transverse sectional view taken substantially on a plane indicated by section line 3-3 in FIG.

FIG. 4 is a partial sectional view taken substantially on a plane indicated by section line 44 in FIG. 3;

FIG. 5 is a partial side sectional view taken substantially on a plane indicated by section line 5 5 in FIG.

draulic device 10 includes a cylinder housing assembly generally referred to by reference numeral 12 which is adapted to be fixedly mounted in a vertical position. The cylinder assembly includes an outer casing 14 secured as by welding 16 at its lower axial end to a semispherical head 18. The casing issecured at its upper end by welding 20 to an upper head assembly 22 of a type disclosed in my prior US. Pat. No. 3,416,406. By means of the upper head assembly 22, fluid under pressure is introduced into the cylinder cavity 24. The upper head assembly accordingly includes an annular manifold 26 and is operative to decelerate and stop upward extension of a ram assembly 28 in wiping engagement with a slide bearing assembly 29 through. which the ram assembly projects.

The ram assembly 28 includes an elongated tubular member 30 enclosing a pressure chamber 32. The pressure chamber is closed at its upper end by a pressure head 34 having a removable plug 36. Closely spaced above the pressure head 34 and welded to the tubular member 28, is an annular bolt ring 38 through which a load may be anchored to the upper endof the ram assembly. The lower end of the tubular member 30 is secured by welding at 40 to a piston block member 42 having a stop shoulder 44 between a smaller diameter portion 46 flush with the ram member 30 and a larger diameter portion 48. The block member 42 cooperates with the upper head assembly 22 for decelerating and stopping movement of the ram assembly as described and explained in detail in my prior U. S. Pat. No. 3,416,406, aforementioned. The block member 42 furthermore is formed with an inner bore 50 communicating with an.-annular recess 52 at the lower end thereof. A retainer plate 54 is secured to the lower end of the block member 42 by a plurality of fasteners 56 and forms a pressure face at the lower end of the ram assembly causing upward extension of the ram assembly from the cylinder in response to pressurization of the cylinder cavity 24 by fluid under pressure introduced through the upper head assembly 22. The retainer plate 54 furthermore retains an orifice ring 58 floatingly within the recess 52 for purposes to be explained hereafter.

The block member 42 is also provided with a vent passage 60 that extends from the larger diameter portion 48 to the upper axial end thereof so as to establish fluid communication between the cylinder cavity 24 and a vent tube 62 secured at its lower end to the block member 42. The vent tube extends upwardly from the block member within the tubular ram member 30 to a location spaced closely below the pressure head plate 34. As will be explained hereafter, the vent tube 62 conducts gases such as air collected at the upper end of the pressure chamber 32 into the cylinder cavity 24.

While the ram assembly is guided for vertical move ment along the longitudinal axis of the cylinder assembly by means of the slide bearing 29, it is positioned at its lower end by the block member 42 about a tubular positioning column 64. The tubular column is fixed to the cylinder assembly by being welded at its lower end to a safety head plate 66 closely spaced above the lower end of the casing 14 and welded thereto. The safety head plate is provided with a relief port 68 and to prevent it from being separated from the main casing body 14, it is peripherally formed with notches 70 as more clearly seen in FIG. 3 so as to receive a plurality of attachment plates 72 that are welded internally to the casing adjacent the lower end and extend axially beyond the safety head plate 66 as more clearly seen in FIG. 4. The safety head plate in addition to fixedly anchoring the tubular column 64, closes the lower end of an axially elongated passage 74 formed within the column. The passage 74 is in continuous and unrestricted fluid communication with the ram pressure chamber 32 through an opening 76 formed in the plate 78 at the upper end of the column.

The tubular column 64 is formed with orifice ports 80 through which fluid communication is established between the ram pressure chamber 32 and the cylinder cavity 24 as the ram is descending toward its lower position as shown in FIG. 6. When the ram reaches its lower position as shown in FIGS. 2 and 5, fluid communication through the passage 74 is blocked. Accordingly, any excess pressure within the chamber 32 over that in the cylinder cavity 24 will cause restricted flow through the annular passage 82 formed within the bore 50 of the block member 42 and the restricted annular passage 84 formed between the floating orifice ring 58 within the recess 52 and the column. Thus, by proper selection of the orifice ring dimension, the rate of restricted flow may be predetermined for any particular pressure differential condition. Further, the tubular column may be shaped differently from the cylindrical configuration shown. The column may be conical, for example. However, the column must have an externally smooth and continuous surface to position the ram at its lower end.

It will be apparent that the orifice ports 80 are operative to equalize pressures within the ram chamber 32 and cylinder cavity 24 while the ram assembly is being extended or retracted and are dimensioned so as to have no significant affect on normal operation of the hydraulic device during supply of fluid under pressure to the cylinder cavity and release of pressure therefrom in order to effect extension of the ram and retraction thereof under load. It will be furthermore apparent that as the ram assembly descends from its extended position, there will be a volumetric contraction of the pressure chamber 32 enclosed therein which would produce a build-up of pressure if not for the pressure equalizing flow through the orifice ports 80 which are dimensioned to prevent any substantial build-up of pressure under controlled normal operating conditions as aforementioned. However, should there be any uncontrolled leakage from the cylinder casing 14 due to corrosion, for example, or from the fluid line to the hydraulic device as a result of rupture, for example, downward descent of the ram assembly will be decelerated by virtue of the restriction to flow offered by the orifice ports 80. The flow area of the orifice ports 80 therefore decreases and is more widely spaced in a downward direction so as to offer a progressively increasing restriction to pressure equalizing flow as the ram assembly descends to its lower position. When the ram assembly approaches its lower position, the orifice ports are completely blocked so that any pressure equalizing flow must proceed through the restricted passage 84 formed by the orifice ring 58. The orifice ring 58 may therefore be dimensioned in order to provide the desired final degree of deceleration.

The vent tube 62 constitutes an additional feature by means of which any accumulation .of air or other gases at the upper end of the pressure chamber 32 in the ram assembly, may be conducted together with operating fluid into the cylinder cavity 24.

The principles of the present invention may be applied to a pair of decelerating snubber devices 86 associated with a hydraulic elevator 88 as shown in FIG. 7. The snubber devices 86 are located on opposite sides of the hydraulic elevator device 88 from which the ram 90 extends upwardly and supports a load platform 92. The ram 90 is extended together with the rams 92 associated with the snubber devices 86 by fluid under pressure supplied to the upper ends of the associated cylinder assemblies through fluid branch lines 94, 96 and 98. Fluid under pressure is supplied to the branch lines through the supply line 100 connected by the check valve 102 to the output of a motor driven pump 104. Pressure is released within the cylinder assemblies associated with the hydraulic device 88 and the snubber devices 86 by opening of the lowering valve 106. Flow through the branch lines 94 and 98 is regulated relative to the main branch line 96 by externally controlled flow valves 108 and 110. Should there be any uncontrolled descent of the ram 90 due to emergency conditions as aforementioned, the load platform 92 when approaching its lower position will engage the shock absorbing elements 112 on the upper ends of the rams 92 associated with the snubber devices 86. The rams 92 will then descend into the associated cylinder assemblies to decelerate further downward descent of the load platform in a manner similar to that hereinbefore described with respect to the hydraulic device 10.

As shown in FIG. 8, each of the snubber devices 86 includes a piston head 114 connected to the lower end of the ram 92 within the cylinder casing 116 which is provided with a safety head 118 at its lower end to which the column 120 is secured. The column is provided with orifice ports 122 similar in function and operation to the orifice ports 80 hereinbefore described in order to progressively restrict pressure equalizing flow between the elongated passage 124, which is in continuous communication with the ram pressure chamber 126, and the cylinder cavity 128 to which one of the branch lines 94 and 98 is connected.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

What is claimed as new is as follows:

1. In combination with a fluid pressure device having a housing enclosing a cavity, a ram having a piston, and means internally pressurizing the cavity with a fluid on opposite sides of the piston for extension of the ram from the housing, means for decelerating retraction of the ram in response to uncontrolled leakage of fluid from the cavity, comprising a ram positioning member fixed to the housing and enclosing a passage closed by the ram, flow restriction means mounted within the piston in surrounding relation to the positioning member for establishing continuous restricted fluid communciation between the passage and the cavity to equalize pressures within the ram and the cavity, and orifice means mounted within the positioning member forvpro gressively restricting fluid communication between the passage and the cavity externally of the ram during said retraction of the ram. I

2. The combination of claim 1 wherein said housing comprises an outer casing having opposite axial ends, a safety head fixed to said casing adjacent one of said ends to which the positioning member is connected, and a bearing assembly connected to the casing adjacent the other of the ends through which the ram slidably extends.

3. In combination with a fluid pressure device having a housing, a ram, and means internally pressurizing the housing with a fluid for extension of the ram from the housing, means for decelerating retraction of the ram in response to uncontrolled leakage of fluid, comprising elongated passage means fixed to the housing and disposed internally of the ram for continuous unrestricted fluid communication with the ram internally thereof, and orifice means mounted by the passage means for progressively restricted fluid communication between the passage means and the housing externally of the ram during said'retraction of the ram, said housing comprising an outer casing having opposite axial ends, a safety head fixed to said casing adjacent one of said ends to which the elongated passage means is connected, and a bearing assembly connected to the casing adjacent the other of the ends through which the ram slidably extends, a plurality of attachment plates internally secured to the casing adjacent said one of the ends in axially spaced relation to said other of the ends, said safety head being peripherally notched to receive said attachment plates which extend axially therethrough.

4. The combination of claim 3 wherein said ram includes a tubular member having opposite axial end portions, a pressure head secured to the member adjacent one of said end portions extended from the housing enclosing a pressure chamber internally of the ram and a piston assembly connected to the member adjacent the other of the end portions within the housing substantially sealing said pressure chamber from a cavity enclosed by the housing externally about the ram.

5. The combination of claim 4 including venting means internally mounted by the ram for conducting gas accumulated within the pressure chamber adjacent the pressure head to the cavity adjacent the piston assembly.

6. The combination of claim 5 wherein the elongated passage means comprises a tubular column closed at one end and opened at the other end, said column having an external slide bearing surface on which the ram is positioned.

7. The combination of claim 6 wherein said orifice means comprises a plurality of pressure equalizing ports formed in said column, said ports decreasing in flow area as a function of the distance from the closed end of the column.

8. The combination of claim 7 wherein said piston assembly includes a slide block having an annular recess surrounding the elongated passage means, and an orifice ring seated in said recess forming a restricted axial passage between the housing cavity and the pressure chamber in the ram.

9. The combination of claim 2 wherein said ram includes a tubular member having opposite axial end portions, a pressure head secured to the member adjacent one of said end portions extended from the housing enclosing a pressure chamber internally of the ram, said piston being connected to the member adjacent the other of the end portions within the housing substantially sealing said pressure chamber from the cavity en closed by the housing externally about the ram.

110. In combination with a fluid pressure device having a housing, a ram, and means internally pressurizing the housing with a fluid for extension of the ram from the housing, means for decelerating retraction of the ram in response to uncontrolled leakage of fluid, comprising elongated passage means fixed to the housing and disposed internally of the ram for continuous unrestricted fluid communication with the ram internally thereof, and orifice means mounted by the passage means for progressively restricted fluid communication between the passage means and the housing externally of the ram during said retraction of the ram, said housing comprising an outer casing having opposite axial ends, a safety head fixed to said casing adjacent one of said ends to which the elongated passage means is connected, and a bearing assembly connected to the casing adjacent the other of the ends through which the ram slidably extends, said ram including a tubular member having opposite axial end portions, a pressure head secured to the member adjacent one of said end portions extended from the housing enclosing a pressure chamber internally of the ram and a piston assembly connected to the member adjacent the other of the end portions within the housing substantially sealing said pressure chamber from a cavity enclosed by the housing externally about the ram, said piston assembly including a slide block having an annular recess surrounding the elongated passage means, and an orifice ring seated in said recess fonning a restricted axial passage between the housing cavity and the pressure chamber in the ram.

11. The combination of claim 10 including venting means internally mounted by the ram for conducting gas accumulated within the pressure chamber adjacent the pressure head to the cavity adjacent the piston assembly.

12. The combination of claim 9 including venting means internally mounted by the ram for conducting gas accumulated within the pressure chamber adjacent the pressure head to the cavity adjacent the piston assembly.

13. The combination of claim 1 wherein the positioning member comprises a tubular column closed at one end and opened at the other end, said column having an external slide bearingsurface on which the ram is positioned.

14. The combination of claim 13 wherein said orifice means comprises a plurality of pressure equalizing ports formed in said column, said ports decreasing in flow area as a function of the distance from the closed end of the column.

end of the column.

17. The combination of claim 1 wherein said flow restriction means includes an annular recess formed within the piston in surrounding relation to the positioning member, and an orifice ring seated in said recess forming a restricted axial passage between the cavity and a pressure chamber enclosed by the ram about the positioning member. 

1. In combination with a fluid pressure device having a housing enclosing a cavity, a ram having a piston, and means internally pressurizing the cavity with a fluid on opposite sides of the piston for extension of the ram from the housing, means for decelerating retraction of the ram in response to uncontrolled leakage of fluid from the cavity, comprising a ram positioning member fixed to the housing and enclosing a passage closed by the ram, flow restriction means mounted within the piston in surrounding relation to the positioning member for establishing continuous restricted fluid communciation between the passage and the cavity to equalize pressures within the ram and the cavity, and orifice means mounted within the positioning member for progressively restricting fluid communication between the passage and the cavity externally of the ram during said retraction of the ram.
 2. The combination of claim 1 wherein said housing comprises an outer casing having opposite axial ends, a safety head fixed to said casing adjacent one of said ends to which the positioning member is connected, and a bearing assembly connected to the casing adjacent the other of the ends through which the ram slidably extends.
 3. In combination with a fluid pressure device having a housing, a ram, and means internally pressurizing the housing with a fluid for extension of the ram from the housing, means for decelerating retraction of the ram in response to unControlled leakage of fluid, comprising elongated passage means fixed to the housing and disposed internally of the ram for continuous unrestricted fluid communication with the ram internally thereof, and orifice means mounted by the passage means for progressively restricted fluid communication between the passage means and the housing externally of the ram during said retraction of the ram, said housing comprising an outer casing having opposite axial ends, a safety head fixed to said casing adjacent one of said ends to which the elongated passage means is connected, and a bearing assembly connected to the casing adjacent the other of the ends through which the ram slidably extends, a plurality of attachment plates internally secured to the casing adjacent said one of the ends in axially spaced relation to said other of the ends, said safety head being peripherally notched to receive said attachment plates which extend axially therethrough.
 4. The combination of claim 3 wherein said ram includes a tubular member having opposite axial end portions, a pressure head secured to the member adjacent one of said end portions extended from the housing enclosing a pressure chamber internally of the ram and a piston assembly connected to the member adjacent the other of the end portions within the housing substantially sealing said pressure chamber from a cavity enclosed by the housing externally about the ram.
 5. The combination of claim 4 including venting means internally mounted by the ram for conducting gas accumulated within the pressure chamber adjacent the pressure head to the cavity adjacent the piston assembly.
 6. The combination of claim 5 wherein the elongated passage means comprises a tubular column closed at one end and opened at the other end, said column having an external slide bearing surface on which the ram is positioned.
 7. The combination of claim 6 wherein said orifice means comprises a plurality of pressure equalizing ports formed in said column, said ports decreasing in flow area as a function of the distance from the closed end of the column.
 8. The combination of claim 7 wherein said piston assembly includes a slide block having an annular recess surrounding the elongated passage means, and an orifice ring seated in said recess forming a restricted axial passage between the housing cavity and the pressure chamber in the ram.
 9. The combination of claim 2 wherein said ram includes a tubular member having opposite axial end portions, a pressure head secured to the member adjacent one of said end portions extended from the housing enclosing a pressure chamber internally of the ram, said piston being connected to the member adjacent the other of the end portions within the housing substantially sealing said pressure chamber from the cavity enclosed by the housing externally about the ram.
 10. In combination with a fluid pressure device having a housing, a ram, and means internally pressurizing the housing with a fluid for extension of the ram from the housing, means for decelerating retraction of the ram in response to uncontrolled leakage of fluid, comprising elongated passage means fixed to the housing and disposed internally of the ram for continuous unrestricted fluid communication with the ram internally thereof, and orifice means mounted by the passage means for progressively restricted fluid communication between the passage means and the housing externally of the ram during said retraction of the ram, said housing comprising an outer casing having opposite axial ends, a safety head fixed to said casing adjacent one of said ends to which the elongated passage means is connected, and a bearing assembly connected to the casing adjacent the other of the ends through which the ram slidably extends, said ram including a tubular member having opposite axial end portions, a pressure head secured to the member adjacent one of said end portions extended from the housing enclosing a pressure chamber internally of the ram and a piston assembly connecTed to the member adjacent the other of the end portions within the housing substantially sealing said pressure chamber from a cavity enclosed by the housing externally about the ram, said piston assembly including a slide block having an annular recess surrounding the elongated passage means, and an orifice ring seated in said recess forming a restricted axial passage between the housing cavity and the pressure chamber in the ram.
 11. The combination of claim 10 including venting means internally mounted by the ram for conducting gas accumulated within the pressure chamber adjacent the pressure head to the cavity adjacent the piston assembly.
 12. The combination of claim 9 including venting means internally mounted by the ram for conducting gas accumulated within the pressure chamber adjacent the pressure head to the cavity adjacent the piston assembly.
 13. The combination of claim 1 wherein the positioning member comprises a tubular column closed at one end and opened at the other end, said column having an external slide bearing surface on which the ram is positioned.
 14. The combination of claim 13 wherein said orifice means comprises a plurality of pressure equalizing ports formed in said column, said ports decreasing in flow area as a function of the distance from the closed end of the column.
 15. The combination of claim 9 wherein the positioning member comprises a tubular column closed at one end and opened at the other end, said column having an external slide bearing surface on which the ram is positioned.
 16. The combination of claim 15 wherein said orifice means comprises a plurality of pressure equalizing ports formed in said column, said ports decreasing in flow area as a function of the distance from the closed end of the column.
 17. The combination of claim 1 wherein said flow restriction means includes an annular recess formed within the piston in surrounding relation to the positioning member, and an orifice ring seated in said recess forming a restricted axial passage between the cavity and a pressure chamber enclosed by the ram about the positioning member. 